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  Copyright (c) 2015-2018 Jean-Marc VIGLINO, 
  released under CeCILL-B (french BSD like) licence: http://www.cecill.info/
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  <title>ol-ext: hash lines example</title>
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  <meta name="description" content="an OL3 stroke style with a set of cartographic patterns to use in your maps." />
  <meta name="keywords" content="ol3, vector, style, stroke, fill, pattern, hatch, hatching" />

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  <a href="https://github.com/Viglino/ol-ext" class="icss-github-corner"><i></i></a>

  <a href="../../index.html">
    <h1>ol-ext: hash lines example</h1>
  </a>
  <div class="info">
    <p>
      This example use the <i>ol.coordinate.offsetCoords()</i> function to draw an offset line with a dash symbol.
    </p>
    <p>
      NB: some problem may occur when offsetting lines with acute convex angles... 
      You should probably look at <a href="https://openlayers.org/en/latest/examples/jsts.html">JSTS</a> to handle this cases.
    </p>
  </div>

  <!-- Map div -->
  <div id="map" style="width:600px; height:400px;"></div>

  <div class="options" style="min-width:300px;">
    <h2>Options:</h2>
    <ul>
      <li>
        Draw:
        <label>
          <input type="radio" name="op" value="drawPoly" /> 
          Polygon
        </label>
        <label>
          <input type="radio" name="op" checked="checked" value="drawLine" /> 
          LineString
        </label>
        <label>
          <input type="radio" name="op" value="modify" /> 
          Modify
        </label>
      </li>
      <li>
        <hr/>
        Offset: <input id="offset" type="number" value=5 onchange="vector.changed()" />
      </li>
    </ul>
  </div>
  
<script type="text/javascript">
  
  // Layers
  var layer = new ol.layer.Geoportail({ layer: 'ORTHOIMAGERY.ORTHOPHOTOS' });

  // The map
  var map = new ol.Map({
    target: 'map',
    view: new ol.View ({
      zoom: 5,
      center: [166326, 5992663]
    }),
    layers: [layer]
  });

  // Offset geometry
  function offsetGeometry (feature, size) {
    switch (feature.getGeometry().getType()) {
      case 'Polygon':
        var coords = feature.getGeometry().getCoordinates();
        var sign = feature.getGeometry().getLinearRing(0).getArea() < 0 ? -1 : 1;
        coords[0] = ol.coordinate.offsetCoords(coords[0], sign*size);
        return new ol.geom.Polygon(coords);
      case 'LineString':
        var coords = feature.getGeometry().getCoordinates();
        coords = ol.coordinate.offsetCoords(coords, size);
        return new ol.geom.LineString(coords);
      default:
        return feature.getGeometry();
    }
  }
  
  // Style function with offset hash
  function getStyle(feature, res){
    var offset = parseInt($("#offset").val());
    return [ 
      new ol.style.Style({
        stroke: new ol.style.Stroke({	
          width: 1.5,
          color: "#8B4513"
        })
      }),
      new ol.style.Style({
        stroke: new ol.style.Stroke({	
          color: "#8B4513",					
          width: offset>0 ? 2*offset : -2*offset,
          lineDash:[1.5,10],
          lineCap:'butt',
          lineJoin:'bevel'
        }),
        // Offset geometry
        geometry: function (feature) { return offsetGeometry(feature, offset*res); }
      })
    ];
  }

  // Nouvelle source de donnee
  var vector = new ol.layer.Vector({
    source: new ol.source.Vector({ features: new ol.Collection() }),
    style: getStyle
  })
  map.addLayer(vector);
  vector.getSource().addFeature(new ol.Feature(new ol.geom.Polygon([[[259274, 6398696], [63595, 5958419], [635956, 5772524], [259274, 6398696]]])));

  // global so we can remove it later
  var interactions = {
    select: new ol.interaction.Select (),
    modify: new ol.interaction.Modify ({ features: vector.getSource().getFeaturesCollection() }),
    drawLine: new ol.interaction.Draw({
      type: 'LineString',
      source: vector.getSource()
    }),
    drawPoly: new ol.interaction.Draw({
      type: 'Polygon',
      source: vector.getSource()
    })
  }
  for (var i in interactions) map.addInteraction(interactions[i]);

  // Activate interaction
  setInteraction = function() {
    //interactions.select.getFeatures().clear();
    var name = $('[name="op"]:checked').val();
    for (var i in interactions) {
      interactions[i].set("active", (i==name));
    }
  }
  setInteraction();
  $("input:radio").on("change",setInteraction);

</script>

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